Rubber adhesion bonding

Mechanical stability of the copper sulfide domains is essential to retain long-term durability of the rubber-to-wire adhesion. However, corrosion of the wire-rubber adhesive bond is catalyzed by Zn + ions that diffuse through the interfacial CuS layer. This will eventually result in an excess of either ZnS or ZnO/Zn(OH)2. Under dry conditions, this process is slow. Nevertheless, Zn + will migrate to the surface with a consequent drop in mechanical interlocking of the CuS domains and rubber followed by adhesion loss. 

One of the most common rubber adhesives are the contact adhesives. These adhesives are bonded by a diffusion process in which the adhesive is applied to both surfaces to be joined. To achieve optimum diffusion of polymer chains, two requirements are necessary (1) a high wettability of the adhesive by the smooth or rough substrate surfaces (2) adequate viscosity (in general rheological properties) of the adhesive to penetrate into the voids and roughness of the substrate surfaces. Both requirements can be easily achieved in liquid adhesives. Once the adhesive solution is applied on the surface of the substrate, spontaneous or forced evaporation of the solvent or water must be produced to obtain a dry adhesive film. In most cases, the dry-contact adhesive film contains residual solvent (about 5-10 wt%), which usually acts as a plasticizer. The time necessary... 

Silicones. Silicones are useful where high temperature resistance or compatibility with silicone components such as molded seals are needed. Silicone firewall insulation materials and silicone gaskets and seals are bonded with silicone rubber adhesives. 

Copper-zinc Copper-zinc alloys are deposited for two main purposes (a) as a decorative finish, e.g. on steel and (b) as a means of obtaining an adhesive bond of rubber to other metals. 

An examination is made of a European Union directive aimed at limiting emissions of volatile organic compounds arising from the industrial use of organic solvents. Proposed emission limits applicable to the use of solvents in coatings, inks and adhesives manufacture, adhesive bonding and rubber processing are presented. 

Control of fiber friction is essential to the processing of fibers, and it is sometimes desirable to modify fiber surfaces for particular end-uses. Most fiber friction modifications are accomplished by coating the fibers with lubricants or finishes. In most cases, these are temporary treatments that are removed in final processing steps before sale of the finished good. In some cases, a more permanent treatment is desired, and chemical reactions are performed to attach different species to the fiber surface, e.g. siliconized slick finishes or rubber adhesion promoters. Polyester s lack of chemical bonding sites can be modified by surface treatments that generate free radicals, such as with corrosive chemicals (e.g. acrylic acid) or by ionic bombardment with plasma treatments. The broken molecular bonds produce more polar sites, thus providing increased surface wettability and reactivity. 

ISO 5893 2002 Rubber and plastics test equipment - Tensile, flexural and compression types (constant rate of traverse) - Specification ISO 6237 2003 Adhesives - Wood-to-wood adhesive bonds - Determination of shear strength by tensile loading... 

Moisture acts as a debonding agent through one of or a combination of the following mechanisms 1) attack of the metallic surface to form a weak, hydrated oxide interface, 2) moisture assisted chemical bond breakdown, or 3) attack of the adhesive. (2 ) A primary drawback to good durability of metal/adhesive bonds in wet environments is the ever present substrate surface oxide. Under normal circumstances, the oxide layer can be altered, but not entirely removed. Since both metal oxides and water are relatively polar, water will preferentially adsorb onto the oxide surface, and so create a weak boundary layer at the adhesive/metal interface. For the purposes of this work, the detrimental effects of moisture upon the adhesive itself will be neglected. The nitrile rubber modified adhesive used here contains few hydrolyzable ester linkages and therefore will be considered to remain essentially stable. 

Asphalt—mbber is mixed and applied to roadways by several techniques. In one method, mbber and asphalt are mixed at ca 175—220°C for one to two hours. The hot mixture is applied to the roadway and covered with a layer of stone chips to form a chip seal. The mbber cmmb consists of scrap tires ground into particles less than 2 mm in diameter. Rubber-modified asphalt is also used for waterproofing membranes, crack-and-joint sealers, hot-mix binders, and roofing materials. The mbber improves asphalt ductility and increases its softening point. The aggregate adhesive bond is stronger, and the asphalt lasts longer. Production of rubber-modified asphalt has increased from 405 t in 1970 to 27,000 t in 1980 (41). Typically, about 2 t of mbber is used for 1 km of roadway. If it is assumed that asphalt—mbber contains ca 25% mbber and 75% asphalt, the potential demand for scrap mbber would be ca 40,500 t/yr, or ca 2% of the amount available. 

The adhesion of rubber to PET fibers has been studied using FT-IR 278,279). The kinetics of the chemical reactions occurring with the coupling agent and the end groups of the PET fiber have been measured and the results extrapolated to a quantitative determination of the adhesive bonding during fabrication 278,279). 

Araldlte is an epoxy resin bonding agent, made by Bond Master Rubber Adhesive Co, Irving con, Nj, used in some US elec detonators, such as the T44. In this item, the pin and the inside of the plug are coated with Formvar for insulation and then bonded together with Araldite... 

Tyres are very definitely fatigued during use and, as mentioned for fabric/rubber adhesion above, it is very important to carry out dynamic tests to assess bond efficiency. Methods have not apparently been standardised but a variety of procedures have been reported71 79 Some workers have used the same or a similar test piece as in static tests and applied a cyclic tensile stress or strain, whilst others have used some form of fatigue tester operating in compression/shear to repeatedly stress or strain cord/rubber composite, or even to flex samples in the form of a belt. Khromov and Lazareva80 describe a method using test pieces cut from tyres. 

Woo et al. (1994) studied a DGEBA/DDS system with both polysul-fone and CTBN. The thermoplastic/rubber-modified epoxy showed a complex phase-in-phase morphology, with a continuous epoxy phase surrounding a discrete thermoplastic/epoxy phase domain. These discrete domains exhibited a phase-inverted morphology, consisting of a continuous thermoplastic and dispersed epoxy particles. The reactive rubber seemed to enhance the interfacial adhesive bonding between the thermoplastic and thermosetting domains. With 5 phr CTBN in addition to 20 phr polysul-fone, Glc of the ternary system showed a 300% improvement (700 Jm-2 compared with 230 J m 2 for the neat matrix). 

A silicone rubber adhesive layer is used in US-A-4081819 to bond an HgCdTe substrate, which includes an epitaxial layer, to a second substrate. The silicone rubber adhesive reduces the risk that the substrate cracks when cooled to cryogenic temperatures. 

An HgCdTe epitaxial layer is patterned to form individual devices 10a, 10b and 10c on a substrate 12 of HgCdTe. The substrate is bonded to a second substrate 14 by a silicone rubber adhesive 16. 

Plasticizer migration from the vinyl part into the adhesive bond line can degrade the strength of the joint. Adhesives must be tested for their ability to resist the plasticizer. PVC can be made with a variety of plasticizers. An adhesive suitable for a certain flexible PVC formulation may not be compatible with a PVC from another supplier. Nitrile rubber adhesives have been found to be very resistant to plasticizers and are often the preferred adhesive for flexible PVC films. However, certain epoxy adhesive formulations have also been found to provide excellent adhesion to flexible PVC substrates. Several such starting formulations are presented in Table 16.7. A comparison of the performance of several classes of adhesive when bonding PVC to itself and to various other materials is given in Table 16.15. 

Elastomer materials specifications usually do not focus on the adhesive properties, but mainly address the chemical and physical properties of the rubber. Thus, the supplier has wide latitude within the specification to make changes in the compound formulation that could be disastrous to the adhesive bond. One solution is to qualify every new lot of elastomer material for adhesion as well as the more standard properties. 

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